Losing FC

[Mam262]

Hello,

Since opening my pool 2 weeks ago I have not been able to maintain my FC.

After testing it a few times and seeing my FC almost 0 I decided to SLAM assuming I had alge growing even though the pool was clear. My one problem is I had already added CYA prior to realizing I was losing my FC so it is making my SLAM expensive due to the high amounts of chlorine I have to buy. I have been holding FC at 38-40 for 2 days and it held overnight last night. Then I just checked it now and I lost 1/2 of my FC. Below are my numbers.

Yesterday after sundown:
FC: 40
CC 0.5
CYA 80
TA 60
Calcium 375

This Morning before sunrise
FC: 38
CC 0.5
CYA 80
TA 60
Calcium 375

Tonight after sundown:
FC 22.5
CC 0.5
CYA 80
TA 60
Calcium 375

Can anyone help me with why I would have lost so much FC all of a sudden?

Thank you,
Mike

 

[JamesW]

Re: Losing FC

You're going to lose fc during the day due to uv light.

Just pass the OCLT and you're good.

 

[Mam262]

Re: Losing FC

Is it normal to lose that much FC in one day? To go from 38 to 22.5?

 

[JamesW]

Re: Losing FC

With the fc that high, it's normal.

 

[Mam262]

Thank you very much. I will check it again in the morning.

 

[Mam262]

I checked the FC in the morning and it held steady. Thanks again. I was concerned that by loosing so much FC during the day in meant that something was eating my FC again.